One component I haven't seen discussed here is that you also likely can't use them for anything but entirely off-grid setups. I've heard that in our locality,

One component I haven't seen discussed here is that you also likely can't use them for anything but entirely off-grid setups. I've heard that in our locality, and I think this is pretty common around the US, that they won't permit you, and the utility won't allow grid tie of anything at all sketchy, including UL listed panels you buy used.